1. Technical Field
The present invention relates to a light emitting diode (LED) driving device, and more particularly, to an LED driving device capable of having a compact size, while solving a problem that a degree of scattering of a current increases due to the use of a plurality of amplifiers in driving the LED in a multi-channel driving scheme.
2. Description of the Related Art
A light emitting diode (LED) has been widely used in various fields such as illumination, a backlight unit (BLU), or the like. Recently, as a market of the LED has quickly expanded, the related technology has been rapidly advanced.
Generally, an LED current is mainly set and controlled by conversion dimming signal (ADIM) and resistor (RLED) parameters.
Meanwhile, in a light emitting diode back light unit (LED BLU), a multi-channel driving scheme has been used in order to use partial dimming and scanning functions. At the same time, a linear scheme has been used in order to maintain the same brightness.
The linear scheme is advantageous in terms of a cost. However, in this scheme, in order to constantly maintain currents of LED channels, amplifiers have been respectively used for each channel. Each of the amplifiers indicates unique offset voltage characteristics, such that a degree of scattering of currents between each channel increases, thereby reducing matching characteristics between the channels.
FIG. 1 shows a linear constant current driving scheme of a general multi-channel LED according to the related art.
As shown in FIG. 1, each of the amplifiers has an offset voltage Vos.
Therefore, currents for each channel are determined as given in Equations below. It may be appreciated that all of the currents for each channel become different, such that matching characteristics are reduced.
            I              CH        ⁢                                  ⁢        1              =                  ADIM        ⁢                  -                ⁢                  V                      OS            ⁢                                                  ⁢            1                              R                  I              CH        ⁢                                  ⁢        2              =                  ADIM        ⁢                  -                ⁢                  V                      OS            ⁢                                                  ⁢            2                              R                  I              CH        ⁢                                  ⁢        3              =                  ADIM        ⁢                  -                ⁢                  V                      OS            ⁢                                                  ⁢            3                              R      
In order to improve the matching characteristics of the currents for each channel, a method of providing an additional compensation circuit or designing a multi-stage amplifier may be used. However, this method causes not only an increase in the entire chip size, but also causes an increase in a production cost of a chip.